R1218X [RICOH]
Step-up DC/DC converter for Whilte LED Backlight; 升压型DC / DC转换器用于Whilte LED背光
| 型号： | R1218X |
| 厂家： | 
RICOH ELECTRONICS DEVICES DIVISION |
| 描述： | Step-up DC/DC converter for Whilte LED Backlight |
| 文件： | 总14页 (文件大小：326K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
R1218x SERIES
Step-up DC/DC converter for Whilte LED Backlight
NO.EA-006-1025
OUTLINE
The R1218X Series are PWM control type step-up DC/DC converter ICs with low supply current. The R1218X
is fully dedicated to drive White LED with constant current. Each of these ICs consists of an NMOS FET, an
oscillator, a PWM comparator, a voltage reference unit, an error amplifier, an under voltage lockout circuit
(UVLO), an over-voltage protection circuit (OVP), and so on. The R1218X can drive white LEDs with high
efficiency with low supply current. A diode is built-in the R1218XXX1A, therefore it is possible to drive up to
4LEDs without an external diode. The R1218XXX2A, an external diode is necessary, however, up to 6 serial
LEDs can be driven with the R1218XXX2A.
Constant current can be set with an external resistance value. Dimming control is possible by PWM signal for
CE pin. Feedback voltage is 0.2V, therefore power loss by current setting resistance is small and efficiency is
good. Maximum duty cycle is internally fixed, Typ. 91%. LEDs can be driven from low voltage. Protection circuits
are the current limit of Lx peak current, the over voltage limit of output, and the under voltage lockout function.
Packages are standard SOT23-6 and very tiny PLP1820-6.
FEATURES
• Operating voltage............................................. 1.8V to 5.5V
• Built-in 400mA, 1.5Ω, 20V Nch MOSFET (R1218XXX1A)
• Built-in 400mA, 1.5Ω, 29V Nch MOSFET (R1218XXX2A)
• High Frequency PWM control .......................... Oscillator Frequency 1.2MHz
• Maximum Duty Cycle ....................................... Typ. 91%
• Low Feedback Voltage..................................... Typ. 0.2V
• UVLO Threshold Voltage.................................. Typ. 1.6V (Hysteresis Typ. 0.1V)
• Lx Current limit Protection................................ Typ. 700mA
• Over Voltage Protection (OVP) Threshold ....... Typ. 9.5V(R1218X02XA)
.......................................................................... Typ. 14.0V(R1218X03XA)
.......................................................................... Typ. 18.5V(R1218X04XA)
.......................................................................... Typ. 23.0V(R1218X052A)
.......................................................................... Typ. 27.5V(R1218X062A)
• LED dimming control.....................................by external PWM signal (Frequency 500Hz to 5kHz) to CE pin
.......................................................................by feedback voltage and filtered PWM signal (high frequency)
• Packages.......................................................... SOT23-6 or PLP1820-6
APPLICATION
• White LED Backlight for portable equipment
1
R1218X
BLOCK DIAGRAMS
• R1218XXX1A
V
FB
V
IN
VOUT
LX
Err. Amp
UVLO
PWM Comp
+
–
+
–
R
Q
Switch
Control
S
OVP
Vref
Oscillator
Slope
Compensation
Current
Protect
Current
sense
Σ
Shu
tdown
delay
CE
CE
GND
• R1218XXX2A
V
V
FB
IN
V
L
OUT
X
UVLO
Err. Amp
PWM Comp
+
+
–
R
Q
Switch
Control
–
S
OVP
Vref
Oscillator
Slope
Compensation
Current
Protect
Current
sense
Σ
Shutdown
delay
CE
CE
GND
2
R1218X
SELECTION GUIDE
The OVP threshold voltage and the package for the ICs can be selected at the user's request. The selection
can be available by designating the part number as shown below;
R1218xxxxx-xx ←Part Number
↑
↑
↑
a
b
c
Code
Descriptions
Designation of the package
N: SOT23-6
a
K: PLP1820-6
Designation of OVP threshold and with/without of built-in diode
021A: 9.5V with built-in diode
031A: 14.0V with built-in diode
b
c
041A: 18.5V with built-in diode
052A: 23.0V without built-in diode
062A: 27.5V without built-in diode
Taping type (SOT23-6: TR-F, PLP1820-6: TR)
PIN CONFIGURATIONS
• PLP1820-6
zꢀ SOT23-6
6
5
4
6
5
4
VOUT VIN GND
VFB GND
LX
CE
1
VOUT VIN
CE VFB LX
1
2
3
2
3
PIN DESCRIPTION
• SOT23-6
Pin No
Symbol
Pin Description
1
2
3
4
5
6
CE
VOUT
VIN
Chip Enable Pin
Output Voltage
Power Supply Input Pin
Lx
Switching Pin (Open Drain Output)
Ground Pin
GND
VFB
Feedback Pin
3
R1218X
• PLP1820-6
Pin No
Symbol
CE
Pin Description
1
2
3
4
5
6
Chip Enable Pin
Feedback Pin
VFB
Lx
Switching Pin (Open Drain Output)
Ground Pin
GND
VIN
Power Supply Input Pin
Output Voltage
VOUT
ABSOLUTE MAXIMUM RATINGS
Symbol
Item
Rating
6.5
Unit
V
VIN
VIN Pin Voltage
VCE
CE Pin Voltage
VFB Pin Voltage
-0.3 to VIN+0.3
-0.3 to VIN+0.3
V
VFB
V
R1218XXX1A
-0.3 to 22.0
-0.3 to 32.0
-0.3 to 22.0
-0.3 to 32.0
VOUT
VLX
VOUT Pin Voltage
Lx Pin Voltage
V
V
R1218XXX2A
R1218XXX1A
R1218XXX2A
ILX
PD
Lx Pin Current
1000
mA
R1218NXXXA suspended in air
R1218KXXXA*Note1
-40 to +85
250
880
Power Dissipation
mW
Topt
Tstg
Operating Temperature Range
Storage Temperature Range
°C
°C
-55 to 125
(*Note 1) Mounted on board. Conditions: Board material: FR4 Board Dimensions: 40*40*1.6(mm), Double layer,
Wiring Ratio=50%(Both sides), Thermal via: 0.54mm*30pcs, Wind velocity: 0m/s
ELECTRICAL CHARACTERISTICS
• Common
(Topt=25°C)
Symbol
Item
Conditions
MIN.
TYP.
MAX. Unit
VIN
Operating Input Voltage
Supply Current
1.8
5.5
1.0
3.0
1.7
1.8
V
mA
µA
V
IIN
VIN=5.5V, VFB=0V, Lx at no load
VIN=5.5V, VCE=0V
VIN falling
0.5
0.0
ISTB
Standby Current
VUVLO1 UVLO Detector Threshold
1.5
1.5
600
1.6
VUVLO2
VCEH
VCEL
RCE
UVLO Released Voltage
CE “H” Input Voltage
CE “L” Input Voltage
VIN rising
VUVLO1+0.1
V
VIN=5.5V
V
VIN=1.8V
0.5
V
CE Pull Down Resistance VIN=3.6V
VIN=3.6V
1200
10
1600
kΩ
ms
Tshudn CE Shutdown Delay
4
R1218X
Symbol
Item
Conditions
MIN.
TYP.
MAX. Unit
VFB
VFB Voltage Tolerance
VIN=3.6V
0.19
0.20
0.21
V
ppm
/°C
VFB Voltage Temperature
Coefficient
∆VFB/∆T
VIN=3.6V, -40°C≤Topt≤85°C
±150
IFB
VFB Input Current
VIN=5.5V, VFB=0V or 5.5V
VIN=3.6V, ISW=100mA
-0.1
0.1
µA
Ω
RON
Switch On Resistance
1.5
0.0
R1218XXX1A
R1218XXX2A
VIN=3.6V
VLX=20V
VLX=29V
3.0
3.0
µΑ
µΑ
mA
kHz
%
IOFF
Switch Leakage Current
0.0
ILIM
Switch Current Limit
Oscillator Frequency
400
1000
86
1000
1400
700
fOSC
VIN=3.6V, VOUT=VFB=0V
VIN=3.6V, VOUT=VFB=0V
1200
Maxduty Maximum Duty Cycle
91
V
R1218X021A
8.5
10.5
15.0
20.0
24.5
29.0
9.5
V
R1218X031A
R1218X041A
R1218X052A
R1218X062A
R1218X021A
R1218X031A
R1218X041A
R1218X052A
R1218X062A
13.0
17.0
21.5
26.0
14.0
VIN=3.6V
VOVP1
VOVP2
OVP Detector Threshold
OVP Released Voltage
V
18.5
VOUT rising
V
23.0
V
27.5
VOVP1-0.5
VOVP1-0.75
VOVP1-1.0
VOVP1-1.25
VOVP1-1.5
V
V
VIN=3.6V
V
VOUT falling
V
V
• R1218XXX1A
Symbol
Item
Conditions
IDIODE=100mA
VOUT=20V, VLX=0V
MIN.
TYP.
0.8
MAX.
Unit
V
VF
IR
Diode Forward Voltage
Diode Leakage Current
10
µA
TEST CIRCUITS
Supply Current Test Circuit
UVLO Detector Threshold/ UVLO Released Voltage
VIN
LX
VIN
CE
CE
FB
GND
V
GND
VFB
5
R1218X
VFB Voltage, Oscillator Frequency, Maximum Duty OVP Detector Threshold, OVP Released Voltage
Test Circuit
Test Circuit
VIN
LX
VIN
LX
OUT
CE
CE
V
FB
V
FB
GND
V
GND
TYPICAL APPLICATIONS
R1218X041A
R1218X062A
L1
22uH
L1
22uH
C1
1uF
C2
0.22uF
C1
1uF
V
IN
L
X
V
IN
L
X
C2
0.22uF
CE
V
OUT
CE
V
OUT
GND
VFB
GND
V
FB
R1
10Ω
R1
10Ω
• LED Current setting
LED current can be set with feedback resister(R1)
ILED=VFB/R1
• LED Dimming Control, Softstart
(1) LED dimming control by PWM signal to CE pin
LED dimming control is possible by forcing PWM signal to CE pin. When the power-on or start up with CE pin,
softstart function works, however, after that, if the CE pin is set as "L" and set CE pin "H" again during the shutdown
delay time, softstart function is disabled and starts up fast to normal mode, therefore 200Hz to 5kHz PWM signal is
standard. By the CE pin input, LED turns on and off. Average LED current varies depending on the duty cycle of CE input.
Too high frequency PWM signal is not effective because of its delay.
(2)Dimming control by DC voltage
LED dimming control is also possible by using the DC voltage to VFB pin. LED current is adjustable by DC voltage and
resisters, R1 and R2 in the figure 4.
ILED=(DC-0.2)/R2-0.2/R1
(3)Dimming control by feedback voltage and filtered PWM signal
LED dimming control is also possible by using the feedback voltage and filtered PWM signal. LED current is adjustable
according to the "H" level (VH) and "L" level(VL) of PWM signal and resisters, R1, R2, R3, and R4 in the figure5.Duty
6
R1218X
=0% to 100% PWM signal duty cycle can be used up to the maximum LED current and minimum LED current as in the
next formulas.
ILEDMIN=(0.2-R2*(VH-0.2)/(R3+R4))/R1
ILEDMAX=(0.2-R2*(VL-0.2)/(R3+R4))/R1
For example, supposed that the PWM signal level is set as 2.5V/0V, to adjust the LED current range from 0mA to 20mA
by the duty cycle, our recommendation external components values are, R1=10Ω, R2=5.1kΩ, R3=51kΩ, R4=5.1kΩ or
around.
C3 should be set large enough to regard the PWM signal as adjustable DC voltage by the filter. In this method, higher
frequency control than the frequency against the CE pin can be used for dimming control. For example, if the frequency is
40kHz, 0.1uF or more capacitor is our recommendation value as C3.
Figure 3. Dimming controle by CE pin input
Figure 4. Dimming control by DC voltage
CE
R2
DC
V
FB
VFB
R1
R1
Figure 5. Dimming controle by filtered PWM signal
R2
VFB
R1
R3
VH
VL
C3
R4
• Selection of Inductors
The peak current of the inductor at normal mode can be calculated as next formula:
ILxpeak=1.25×ILED×VOUT/VIN+0.5×VIN×(VOUT-VIN)/(L×VOUT×fOSC)
When the start-up or dimming control by CE pin, transient current flows, the peak current must be equal or less
than the current limit of the IC. The peak current should not beyond the rating current of the inductor. For
example, for 4 serial LED drive from VIN=3.6V, recommendation value of the inductor is 10uH or more.
• Selection of Capacitors
Set 1µF or more value bypass capacitor between VIN pin and the GND like C1 as in the figure above as close as
posible to the IC.
Set 0.22µF or more capacitor between VOUT and the GND like C2 as in the figure above.
7
R1218X
TYPICAL CHARACTERISTICS
1) Efficiency vs. ILED( 2LED) L:LQH32CN220 Topt=25°C
VIN=3.6V
R1218X021A
R1218X021A
VIN=1.8V
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
0
4
8
12
16
20
0
4
8
12
16
20
LED Current ILED (mA)
LED Current ILED (mA)
VIN=4.2V
R1218X021A
100
90
80
70
60
50
40
30
20
10
0
0
4
8
12
16
20
LED Current ILED (mA)
2. Efficiency vs. ILED (3LED) L: LQH32CN220, Topt=25°C
VIN=2.7V
VIN=3.6V
R1218X031A
R1218X031A
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
0
4
8
12
16
20
0
4
8
12
16
20
LED Current ILED (mA)
LED Current ILED (mA)
8
R1218X
VIN=4.2V
R1218X031A
100
90
80
70
60
50
40
30
20
10
0
0
4
8
12
ILED (mA)
16
20
LED
電流
3. Efficiency vs. ILED (4 LED ) L: LQH32CN220, Topt=25°C
VIN=3.6V
R1218X041A
VIN=2.7V
R1218X041A
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
0
4
8
12
16
20
0
4
8
12
16
20
LED Current ILED (mA)
LED Current ILED (mA)
R1218X041A
VIN=4.2V
100
90
80
70
60
50
40
30
20
10
0
0
4
8
12
16
20
LED Current ILED (mA)
9
R1218X
4. Efficiency vs. ILED (6LED) L: LQH32CN220, Diode: CRS02
R1218X062A
VIN=3.6V
R1218X062A
VIN=2.7V
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
0
4
8
12
16
20
0
4
8
12
16
20
LED Current ILED (mA)
LED Current ILED (mA)
VIN=4.2V
R1218X062A
100
90
80
70
60
50
40
30
20
10
0
25℃
0
4
8
12
16
20
LED Current ILED (mA)
5. PWM Dimming Control (2 LED) VIN=3.6V, R1=10Ω
5-1. Duty vs. LED current
Topt=25℃
R1218X021A
25
22.5
20
17.5
15
12.5
10
7.5
5
2.5
0
5kHz
1kHz
200Hz
0
20
40
60
80
100
DUTY (%)
10
R1218X
5-2. Output Voltage Waveform (Topt=25°C)
Fosc=200Hz
Fosc=5kHz
R1218X021A
CE Input Voltage
R1218X021A
25
10
5
25
20
15
10
5
10
5
CE Input Voltage
20
0
15
0
Output Voltage
10
5
Output Voltage
0
0
0
0.04
0.08
0.12
0.16
0.2
0
0.8
1.6
2.4
3.2
4
Time (ms)
Time (ms)
6. PWM Dimming Control (4 LED) VIN=3.6V, R1=10Ω
6-1. Duty vs. LED Current (Topt=25°C)
R1218X041A
25
22.5
20
17.5
15
12.5
10
7.5
5kHz
5
1kHz
2.5
0
200Hz
0
20
40
60
80
100
DUTY (%)
6-2. Output Voltage Waveform
Fosc=200Hz
Fosc=5kH
R1218X041A
R1218X041A
50
10
5
50
10
CE Input Voltage
CE Input Voltage
40
40
30
20
10
0
5
0
0
30
20
Output Voltage
Output Voltage
10
0
0
0.8
1.6
2.4
3.2
4
0
0.04
0.08
0.12
0.16
0.2
Time (ms)
Time (ms)
11
R1218X
7. PWM Dimming Control (6 LED) VIN=3.6V,R1=10Ω
7-1. Duty vs. LED Current (Topt=25°C)
R1218X062A
25
22.5
20
17.5
15
12.5
10
7.5
5
2.5
0
5kHz
1kHz
200Hz
0
20
40
60
80
100
DUTY (%)
7-2. Output Voltage Waveform (Topt=25°C)
Fosc=200Hz
Fosc=5kHz
R1218X062A
R1218X062A
50
10
5
50
40
30
20
10
0
10
5
CE Input Voltage
40
CE Input Voltage
30
0
0
Output Voltage
20
Output Voltage
10
0
0
0.8
1.6
2.4
3.2
4
0
0.04
0.08
0.12
0.16
0.2
Time (ms)
Time (ms)
8. VFB Voltage vs. Temperature
9. UVLO Detector Threshold/Released Voltage vs. Temperature
R1218x041A VIN=3.6V
R1218x041A
0.215
VIN=3.6V
1.7
1.66
1.62
1.58
1.54
1.5
0.21
0.205
0.2
UVLO Released
0.195
0.19
0.185
-50
-25
0
25
50
75
100
-50
-25
0
25
50
75
100
Temperature Topt (°C)
Temperature Topt (°C)
12
R1218X
10. Oscillator Frequency vs. Temperature
11. Maximum duty cycle vs. Temperature
R1218x041A
Vin=3.6V
R1218x041A
Vin=3.6V
99
97
95
93
91
89
87
85
1400
1350
1300
1250
1200
1150
1100
1050
1000
-50
-25
0
25
50
75
100
-50
-25
0
25
50
75
100
Temperature Topt (°C)
Temperature Topt (°C)
12. OVP Detector Threshold/Released Voltage vs. Temperature
13. Supply Current vs. Temperature
R1218x041A
Vin=3.6V
R1218x041A
360
Vin=3.6V
20.5
20
320
280
240
200
160
120
80
19.5
19
OVP Detector
Threshold
18.5
18
OVP Released
Voltage
17.5
17
40
0
16.5
-50
-25
0
25
50
75
100
-50
-25
0
25
50
75
100
Temperature Topt (°C)
Temperature Topt (°C)
14. LX Current Limit vs. Temperature
R1218x041A
1000
Vin=3.6V
900
800
700
600
500
400
300
-50
-25
0
25
50
75
100
Temperature Topt (°C)
13
R1218X
15. OVP Transient Response (Topt=25°C)
R1218X041A
OVP Voltage
R1218X021A
25
20
15
10
5
15
12.5
OVP Voltage
10
7.5
5
2.5
0
0
0
20
40
60
80
100
0
20
40
60
80
100
Time (ms)
Time (ms)
R1218X062A
OVP Voltage
35
30
25
20
15
10
5
0
0
20
40
60
80
100
Time (ms)
16. Efficiency dependence on inductors
VIN=3.6V
R1218X041A [Internal Diode Type]
90
85
80
75
70
65
LQH32CN220K53
LQH32CN100K53
GLF2012T220K
GLF2012T100K
60
55
50
0
5
10
LED Current I [mA]
15
20
LED
14
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